The invention relates to swinging seats such as porch swings or the like.
Porch swings are a fixture of leisurely living. Many people find the slow, gentle swinging action of a porch swing to be very soothing. As a general rule, porch swings that are commercially available are furnished with a pair of ordinary chains for suspending the swing from the porch ceiling. The chains are inextensible and hence do not provide any bounce or springiness to the suspension of the swing.
It is also known to include coil tension springs in the suspension of swinging seats to provide such springiness. Representative examples of such seats are shown in U.S. Pat. Nos. 1,390,502, 3,256,016, 4,138,104, 5,564,987, and 5,984,792.
The present invention seeks to improve upon the types of swinging seats disclosed in the aforementioned patents. In accordance with the present invention, a porch swing or the like is suspended from a pair of suspension members each of which includes a coil spring having two or more different zones providing two or more different initial spring constants. A first zone of the spring provides a relatively low initial spring constant so that the springs are sufficiently stretched to provide the desired amount of bounce or springiness to the seat when a person of relatively low weight such as a child is sitting on the seat. The second zone provides a relatively high initial spring constant so that when a heavier person, or more than one person, sits on the seat the total elongation of the spring is significantly less than it would be if the entire spring had the spring constant of the first zone. Accordingly, the springs provide a desired amount of stretch and springiness for a much wider range of weights supported on the seat than a conventional spring having a single spring constant. In other words, the springs have a nonlinear spring constant, rather than a linear spring constant as a typical coil spring has.
Preferably, the springs are barrel shaped having a maximum coil diameter at the middles of the springs and tapering to minimum coil diameters at the two ends of the springs. The largest coils at the middle of the spring provide a relatively low initial spring constant (i.e., the spring constant that applies when the coils are stretched apart starting from an unstretched condition). The smallest coils at the ends of the spring provide a relatively high initial spring constant, and thus will not begin to stretch to any significant extent until the largest coils have already undergone a large degree of stretching.